Acrylonitrile-butadiene-1, 3 copolymers stabilized by antimonyl p-phenyl catecholate



Patented Jan. 8, 1952 Harry E. Albert and George E. P. Smith, Jr.,Akron, Ohio, assignors to The Firestone Tire & Rubber Company, Akron,Ohio, a corporation of Ohio No Drawing.

Original application March 30,

1949, Serial No. 84,493. Divided and this application May 29, 1951,Serial No. 229,531

2 Claims. (Cl. 26045.75)

This application is a division of application Serial No. 84,493, filedMarch 30, 1949.

This invention relates to the stabilization of the rubber-likecopolymers of 1,3-butadiene or other conjugated-diene monomer with avinyl mono.- mer, e. g., acrylonitrile, methacrylonitrile, alphachloroacrylonitrile, propacrylonitrile, acrylamide, esters of acrylicacid and its homologues which contain one to five carbons in the estergroup, etc. The stabilizer used is an antimonyl derivative of p-phenylcatechol in which the hydrogens of the two ortho-hydroxy groups arereplaced by antimony. The invention includes the stabilizedpolymerizates, both cured and uncured, and the process of stabilization.A particular application of the invention is in the stabilization ofrubber compounds which are White or pastel shadesfor example, the whitesidewalls of tires, etc. because the stabilizer of this invention doesnot discolor.

Difiiculty has been experienced in finding a satisfactorynon-discoloring stabilizer for synthetic rubbers.Phenyl-beta-naphthylamine, which is the most widely used stabilizer forGR-S, discolors badly.

Stabi ization of Buna N-type synthetic rubbers Various tests are givenbelow on different Buna N compounds showing the efiect of the stabilizerof this invention and comparing the stabilizer of this invention withphenyl-beta-naphthylamine, the most widely used commercial product. Eachof the stabilized compounds referred to was obtained by adding 2 partsof the stabilizer per 100 parts of copolymer to the latex resulting fromemulsion copolymerization of acrylonitrile and 1,3-butadiene. The latexwas then coagulated and dried, and the samples for tests on thevulcanizate were prepared by vulcanization of such dried coagulum. Thehand tests given in the following table were made by pulling and feelingthe copolymer to detect any stiffening or softening or other sign ofdeterioration.

The commercial stabilizers discolor Buna N- type rubbers badly,particularly on exposure to ultraviolet light. Most of the testsrecorded, therefore, refer to change in color of the products andcompare the color and color change with a control or blank. Table Irefers to tests conducted on a copolymer obtainer by copolymerization of62 per cent butadiene and 32 per cent acrylonitrile.

TABLE I copolymer stabilization Heat-aging at 90 C. Condition afterDrying at 75 C. Stabilizer One Day Four Days Color Hand Test Color HandTest Color Hand Test antlilnioitiyl p-phenyl catc chalky white 110deterioration. cream slightly set up... cream..- set up.

0 o a e. phenyl-beta-naphthylamine. light brown do dark brown. do brownDo.

The stabilizer of this invention may be repre sented as follows:

0 SbOH Antimonyl p-phenyl catecholate polymer, more or less, will givesatisfactory results.

What we claim is:

1. A method of retarding the deterioration ofacrylonitrile-butadiene-l,3 copolymers which comprises incorporatingtherein a small amount of antimonyl p-phenyl catecholate.

2. A composition comprising acrylonitrile-butadiene'-1,3 copolymer and asmall amount of an-- timonyl p-phenyl catecholate.

HARRY E. ALBERT. GEORGE'EQ .1. SMITH, JR.

REFERENCES CITED Number UNITED STATES PATENTS Name Date Hunter Nov. 22,1949

2. A COMPOSITION COMPRISING ACRYLONITRILE-BUTADIENE-1,3 COPOLYMER AND ASMALL AMOUNT OF ANTIMONYL P-PHENYL CATECHOLATE.